LiFePO4 battery and lithium ion polymer battery

Overview

The cycle life of lithium iron phosphate (LiFePO4) battery is four to five times longer than that of other lithium-ion polymer battery. Working temperature range is wider, more safe; But the discharge platform is low, the nominal voltage is only 3.2V, fully charged voltage is 3.65V.

Lithium iron phosphate is used to replace conventional lead acid batteries. We also often find lithium iron phosphate batteries used in home solar systems, fishing, golf carts, outdoor portable energy storage, and electric motorcycles.

What is a lithium iron phosphate battery

Lithium ion polymer (LIPO) batteries

Lithium-ion polymer batteries are rechargeable batteries that rely mainly on the movement of lithium ions between positive and negative electrodes. Lithium-ion batteries use embedded lithium compounds as electrode materials. Currently, lithium ion battery cathode materials commonly used include lithium cobalt acid (LCO battery), lithium manganese acid (LMO battery), terpolymer lithium ion (NCA, NMC battery) and lithium iron phosphate (LiFePO4 battery).

Lithium iron phosphate (LiFePO4, LFP) battery

Lithium iron phosphate battery is a kind of lithium ion polymer battery with lithium iron phosphate as the positive material, graphite carbon electrode as the negative electrode, and metal as the base material.

LiFePO4 battery, also known as LFP battery, is a rechargeable battery. It is currently the safest type of lithium battery on the market. Small size, light weight, cycle life can reach thousands of times.

LiFePO4 battery is different from other lithium ion batteries

Inherits some of the advantages of lithium-ion batteries

High current charging and discharging is one of the advantages of LiPo batteries, which allow the device to release more energy in a short amount of time. These batteries are used more for racing cars and power tools: lithium-ion batteries are used in almost all drones and remote-control models.

RC models typically discharge at 15C, 30C and 50C. Lithium-ion polymer batteries with high discharge rates can reach up to 50C (continuous) and 150C (pulse). They are light, long-lasting, and can be made in a variety of shapes. These are just some of the advantages of lithium ion batteries, and lithium iron phosphate batteries have them.

Long cycle life

cycle life(DOD)

Because the cycle life of LFP batteries is four to five times that of other lithium-ion batteries, it can reach 2,000 to 3,000 cycles or more. The LiFePO4 battery can also achieve a 100% discharge depth (DOD). This means that for energy storage products, LFP batteries do not have to worry about excessive discharge and can even last longer. A good lithium iron phosphate battery lasts three to seven years, so the average cost is very affordable.

For more on depth of discharge (DOD), you can read this article: What is DOD of LiFePO4 Batteries?

However, lithium-iron phosphate batteries have a lower energy density than other lithium-ion batteries, making them unsuitable for wearable devices. In addition, the battery compartment space is limited, so the capacity is relatively low.

As a result, LFP cells are not as durable and compatible with the conditions and interior Spaces of wearables as other LiPo cells.

Why are most lithium iron phosphate batteries 12V?

Lithium iron phosphate batteries are said to be a perfect substitute for lead-acid batteries. The nominal voltage of the lead acid battery is 2V, and the six lead acid batteries in series are 12V.

However, a 12V LiFePO4 battery pack usually consists of four cells in series. The nominal voltage of a single lithium iron phosphate flexible pack battery is 3.2V. When adding the voltage in series, we get 12.8V (3.2V * 4 = 12.8V). There are also commonly used 24V (25.6V) and 48V (51.2V).

In addition, the voltage requirement for most industrial applications is 12V or above, which is the minimum nominal voltage standard for general industrial batteries. There are many applications that need to reach 220V, even 380V or even higher, such as industrial forklifts, winches, electric drills and so on.

In particular, as the sales of 24V and 48V electric forklifts are on the rise recently, the company is focusing on battery safety. Compared with lithium cobalt and lithium manganese, lithium iron phosphate batteries are much safer. The advantage of long life can also reduce the overall cost of battery maintenance and replacement.

Disadvantages of low temperature

Compared with other lithium batteries and lead-acid batteries, the resistance of lithium iron phosphate batteries at low temperature is poor. Generally, the power can only be lowered at -10℃ to -20℃.

However, customers are critical of LFP batteries and their high safety features. They sacrifice some battery performance and specify charging at -30℃ to -40℃. These batteries are mainly used for military or deep-sea and space equipment.

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